Utilization of Combustion Byproducts in Cementitious Materials

Combustion byproducts derived from coal, biomass and waste incineration – notably fly ash, bottom ash and desulfurization slag – have emerged as valuable supplementary cementitious materials. Their incorporation into concrete and mortar can partially replace Portland cement, reducing carbon dioxide emissions and diverting industrial waste from landfill. The fine, often glassy particles of fly ash contribute to pozzolanic reactions, consuming calcium hydroxide and forming additional calcium–silicate–hydrate (C–S–H) gel, which refines pore structure and enhances durability. Circulating fluidized bed combustion ashes, rich in free lime and sulfates, can compensate shrinkage and improve early strength when appropriately processed or blended. Geopolymeric binders utilising high-alkali activation of aluminosilicate-rich ashes offer advanced performance in thermal backfill and aggressive environments. Key challenges include chemical variability, potential for delayed expansion due to free lime or sulphate phases and the need for tailored mix designs. Ongoing research focuses on optimising particle fineness, activation methods and hybrid binder systems to unlock the full environmental and mechanical potential of these byproducts in cementitious matrices.

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Utilization of Combustion Byproducts in Cementitious Materials publication trend

The graph below shows the total number of articles in utilization of combustion byproducts in cementitious materials across all publications each year (not limited to Nature Index journals).

Technical terms

Fly ash: Finely divided residue from coal combustion, rich in silica and alumina, used as a pozzolanic supplementary cementitious material.

Circulating fluidized bed combustion fly ash (CFBFA): Coal ash produced at lower combustion temperatures, containing free calcium oxide and sulphate phases that require specific activation or blending.

Pozzolanic activity: The ability of siliceous or aluminosiliceous materials to react with calcium hydroxide in the presence of water to form cementitious compounds.

Geopolymer: An inorganic binder synthesised by alkali activation of aluminosilicate precursors, forming a three-dimensional polymeric network.

Calcium–silicate–hydrate (C–S–H): The primary hydration product of Portland cement, responsible for strength and microstructural densification in cementitious materials.

References

1. Circulating Fluidized Bed Fly Ash Mixed Functional Cementitious Materials: Shrinkage Compensation of f-CaO, Autoclaved Hydration Characteristics and Environmental Performance. Materials (2021).
2. A Review on the Application of Circulating Fluidized Bed Fly Ash in Building Materials. Advances in Materials Science and Engineering (2022).
3. Analysis of an application possibility of geopolymer materials as thermal backfill for underground power cable system. Clean Technologies and Environmental Policy (2020).